1. Field of the Invention
The present invention relates in general to controlling an electronic display, and more specifically to a method and apparatus for processing temporal and spatial overlapping updates for an electronic display.
2. Description of the Related Art
Electronic visual displays have many forms including active displays which generate light and passive displays which modulate light. Passive displays generally consume less power since they rely upon light reflected from the display to convey visual information rather than light generated by the display, such as a back light or the like. Certain passive displays consume even less power since they are bistable in which they remain in a stable state without additional power input. An electrophoretic display, for example, is a low power passive bistable display. An electrophoretic display is a form of electronic paper (e-paper) or electronic ink display technology which appears similar to ink on paper, and which is commonly used for e-book readers (or e-readers) or the like, such as the Amazon Kindle, the Barnes & Noble Nook, and the Sony Librie, among others. An electrophoretic display utilizes less energy than conventional active displays since it does not have a back light but instead relies upon reflective light for viewing. Electrophoretic displays utilize active-matrix thin-film transistors (TFTs) which are scanned to drive display updates. Once updated, the display remains stable (bistable) so that additional scans are not necessary resulting in additional energy savings. During an update, a waveform is output to the display panel to change one or more pixels from one value to another. Each waveform provided to each pixel being updated spans multiple frame scans, so that the waveform is effectively divided into multiple waveform values in which each value is output to the panel during each frame scan. The present disclosure is illustrated using electrophoretic displays but is applicable to other types of electronic displays.
Each update has to be completed once initiated to avoid an invalid display value, or worse, possible damage or improper operation of the display panel. In certain conventional configurations, a new update is delayed until an existing update is completed. In other conventional configurations, a new update may occur simultaneously with an existing update as long as the regions do not overlap. Any overlapping pixel (i.e., same pixel value belonging to both update regions) caused a conflict so that the current update had to be completed before a new update was initiated.
In order to meet the needs of newer user-interfaces, it is desired that applications using electronic displays support concurrent updates that overlap both spatially and temporally.